Abstract
The objective of this study was to assess the toxicological effect of exposure to benzo(a)pyrene, B[a]P, on germ cells during spermatogenesis. Mice were exposed to B[a]P at 1, 10, 50, and 100 mg/kg/day for 30 days via oral ingestion. Germ cells, including spermatogonia, spermatocytes, pachytene spermatocytes, and round spermatids, were recovered from testes of mice exposed to B[a]P, while mature spermatozoa were isolated from vas deferens. Reproductive organs were collected and weighed. Apoptotic response of germ cells and mature spermatozoa were qualified using the terminal deoxynucleotidyl transferase mediated deoxy-UTP nick end labeling (TUNEL) assay. B[a]P exposure at ≤10 mg/kg/day for 30 days did not significantly alter concentrations of germ cells and mature spermatozoa and apoptotic response in germ cells and mature spermatozoa. Exposure to B[a]P at 50 and 100 mg/kg/day induced testicular atrophy and yielded a significant reduction in the concentrations of spermatogonia, spermatocytes, pachytene spermatocytes, and round spermatid cells as compared with the control. Also, mature spermatozoa experienced decreased concentrations and viability. B[a]P-exposed mice experienced a significant increase in apoptotic germ cells as compared to the control mice. However, the mice dose concentrations were not relevant for comparison to human exposure.
Highlights
Benzo[a]pyrene (B[a]P), a polycyclic aromatic hydrocarbon compound, is produced by incomplete combustion of organic compounds and high-pressure processes
The cross sections of the seminiferous tubules of mice that showed that exposure to B[a]P at 100 mg/kg/day resulted in the atrophy of seminiferous tubules, reduced width of adluminal compartments of the seminiferous tubules, and altered morphology of spermatogonia and spermatocytes (Figure 2)
Only B[a]P at 50 mg/kg/day and 100 mg/kg/day induced a significant decrease in the concentrations of germ cells as compared to the control (P < 0.05)
Summary
Benzo[a]pyrene (B[a]P), a polycyclic aromatic hydrocarbon compound, is produced by incomplete combustion of organic compounds and high-pressure processes. The active intermediates are capable of covalently bonding to DNA [1] and form DNA adducts They can undergo redox cycling and generate excessive reactive oxygen species, which may alter cell signaling and damage cellular membranes resulting in apoptosis [2]. Spermatogenesis represents a complex and dynamic process of proliferation and differentiation of the transformation of spermatogonia into mature spermatozoa in three major stages, the mitotic stage, the meiotic stage, and the maturation stage [6]. Each of these stages represents a key element in the spermatogenic process. The understanding of processes related to spermatogenesis is critical for assessment of male reproductive health
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